Did you even read what aphyr wrote before posting this? It detailed that unlike HTTP, which in general supplies one request per message (GET, POST, etc), a Riemann message contains potentially hundreds of different requests that must be processed individually.
You can put as many "events" in the body of an HTTP POST request as you wish. What really matters in distributed messaging systems, from the performance point of view, is the number of distinct messages per second.
And if a system designer wants to send a stream of "events" to another system to be acted upon, and if this designer cares about throughput (which is assumed here, given the title of the post), then this designer is likely to choose a faster messaging system, especially if it is more flexible, due to its ubiquity and universal support, protocol (e.g. HTTP) over a custom protocol.
